Various metallic articles to be used under abrasive conditions have conventionally been made of intermetallic compound type alloys comprising Ni and/or Co 45-60 atomic % and the remainder Ti and incidental impurities.
Such intermetallic compound type alloys exhibit excellent wear resistance and other mechanical properties for long periods of time, but they are difficult to be machined, especially bored, due to their poor machinability. Therefore, skilful art and much time are necessary to machine the alloy into complicated shapes and such poor machinability increases the cost of production of machined articles.
Additionally, the conventional intermetallic compound type alloys described above tend to absorb oxygen due to high Ti content. As the Ti content increases in the alloy, the embrittlement of the alloy proceeds rapidly to often cause flaws and cracks therein while machined. The alloys, therefore, must be melted and cast in vacuum or in an inert gas atmosphere fully excluding air, not to cause such defects. On the other hand, the raw materials to be melted are desirably of the smallest oxygen content, but some of the commercially available Ti-bearing raw materials often contain more than 500-1,500 ppm of oxygen. The use of such high oxygen Ti-bearing materials inevitably causes a high oxygen content of up to even 1,200-2,000 ppm in the resultant alloy even if the raw materials are melted and cast in vacuum or in an inert gas atmosphere. Such a high oxygen alloy can not be applied to practical use except as scrap due to its extremely low toughness which makes it impossible to be machined.